Open discharge pulp refiner

ABSTRACT

Open discharge, low consistency, paper pulp refiners are provided with refining plates having a pumping or positive beater bar angle to the plate radius of from 5* to 25*, feed grooves in the face of at least one of a plate pair being plugged at the outer plate periphery and the width of the beater bar flow channels sufficient to balance centrifugal flow forces on the pulp stock tending to accelerate said stock therethrough.

United States Patent [191 Leider et a1.

[ Oct. 7, 1975 15 OPEN DISCHARGE PULP REFINER [75] Inventors: Philip J.Leider, Millboro; Jorg Rihs, Clifton Forge, both of Va.

[73] Assignee: Westvaco Corporation, New York,

[22] Filed: May 20, 1974 [21} Appl. No.: 471,473

[52] US. Cl. 24l/261.3; 241/298 [51] Int. Cl. B02C 7/06; B02C 7/12 [58]Field of Search 241/260, 261.2, 261.3, 241/296, 298

[56] References Cited UNITED STATES PATENTS 2,651,976 9/1953 Sutherland241/296 2,654,295 10/1953 Sutherland.....

2,778,282 1/1957 Sutherland. 241/260 X ROTATION 3,049,307 8/1962 Dalzellet a1 241/261.3 X 3,459,379 8/1969 Brown 241/298 X 3,552,664 1/1971Herbert et a1. 241/2613 X Primary Examiner-Granville Y. Custer, Jr.

Assistant Examiner-Howard N. Goldberg Attorney, Agent, or Firm-W. AllenMarcontell; R. L. Schmalz [57] ABSTRACT Open discharge, low consistency,paper pulp refiners are provided with refining plates having a pumpingor positive beater bar angle to the plate radius of from 5 to 25, feedgrooves in the face of at least one of a plate pair being plugged at theouter plate periphery and the width of the beater bar flow channelssufficient to balance centrifugal flow forces on the pulp stock tendingto accelerate said stock therethrough.

12 Claims, 6 Drawing Figures U.S. Patent Oct. 7,1975 Sheet 1 of 23,910,51 1

M- a g US. Patent 00:. 7,1975 Sheet 2 of 2 3,910,511

OPEN DISCHARGE PULP REFINER BACKGROUND OF THE INVENTION 1. Field of theInvention The present invention relates to low consistency wood pulprefiners of the plate or disc type having an open, non-pressurizeddischarge. More specifically, the present invention relates to thebeater bar design configuration of plates having unique utility incombination with such open discharge refiners.

2. Description of the Prior Art In the preparation of wood pulp forpapermaking, cellulosic fibers are subject to a series of mechanicalworking or shearing operations prior to finalweb forming. Depending onthe point in the pulp flow stream where such working takes place, theprocess may be characterized as deshiving, defiberizing, beating orrefining. Furthermore, the range of consistency over which such workingmay be performed spans from approximately 2 to 30 percent; consistencybeing that percentage of dry fiber present in a total aqueous slurry.The art makes a rough distinction between low (generally less thanpercent fiber) and high (generally more than 20 percent fiber)consistency working. Generally, the term refining is used to describelow consistency working in the final process stages immediately prior toweb forming.

The equipment by which paper pulp is refined varies in design as much asthe pulp working conditions. One such design employs fluidpressurization of the refining chamber. If the stock is pumped throughthe refiner against substantial fluid pressure, the process andequipment is known to the art as pressurized refining.

Open discharge refining describes those cases in which the fiber slurry,is discharged from the machine against local atmospheric pressure,usually directly into an unpressurized receiving vessel.

Further differences between pressurized and open discharge refiningmachinery of the disc type are found in the orientation of the bardesign on the plates thereof. Pressurized refiners generally utilize apositive beater bar angle whereas open discharge refiners utilize anegative bar angle.

The term positive angle means that the plate beater bars are angledrelative to the plate radius in a lagging direction. In other words,from a frontal viewing perspective of a pressurized refiner plate, thebars will be angled across the plate plane relative to a plate radius insuch a manner that the outer plate periphery portion of the bar will lagbehind portions of the bar more proximate to the inner plate peripheryrelative to the rotational direction.

Negative angle beater bars are angled relative to the plate radius androtational direction whereby the outer periphery portions of the barslead the inner periphery portions.

When a positive plate angle pattern is reflected in both plates of acooperative pair, the relative shearing movement of a respective pair ofbeater bars imparts a radial outward movement to the stock.

The converse is true of a pair of negative bar plates: e. g. the wipingaction of one beater bar passing in close proximity to a beater bar onthe other plate imparts a radially inward force to the stock.

In the case of the positive angle bars, the bar shearing impetusaugments the natural centrifugal impetus to the stock as a consequenceof plate rotation.

In the case of negative angle bars, the bar shearing impetus counteractsthe centrifugal impetus.

In either case, positive or negative angle bars, the shearing, wipingaction between beater bars on respective plates of a pair is believed tocontribute positively to the stock refining result over the result ofstraight radial bars.

While a net fluid flow pressure differential across the plate face isnecessary to induce flow through any refining engine, regardless of barangle disposition, only in pressurized machines is the pressuredifference a variable that is controlable independently of stock supplypressure. Lacking such independent control over flow pressuredifi'erential, open discharge machines have, historically, been equippedwith negative angle beater bars to restrict the stock flow ratetherethrough. Such flow restriction was deemed necessary to prevent themachine, if provided with positive angle plates, from momentarilydischarging stock at a greater rate than supplied. The consequence of aninstantaneously greater discharge rate is flow cavitation between theplates thereby causing collision or bumping of the plates.

Unfortunately, the magnitude of flow restriction provided by negativeangle platesincreases progressively as the plates wear from use.Accordingly, the stock throughput capacity of a half worn, negativeangle plate is much less than half the new plate capacity.

Although, negative angle plates offer improved refining action overstraight radial plates, it has been discovered that positive angleplates offer even greater improvements. While the tendency of positiveangle plates to bump may be prevented in pressurized machines, the samevehicle of prevention is not available to open discharge machines.Consequently,,to simply equip an open discharge machine with positiveangle plates of prior art design for refining quality gains is to invitethe problems of plate bumping which are predominately represented byexcessive plate wear rates and replacement expenses. Moreover, platebumping can defeat the stock refining quality gains sought by positiveangle plates in the first instance.

The prior use of positive angle plates is taught by US. Pat. Nos.1,160,964, 2,654,295, 3,049,307 and 3,761,027. US. Pat. Nos. 2,651,976and 2,778,282 teach plate patterns that could be adapted to positiveangle disposition.

Assuming that one desired to provide an open discharge refiner withprior art positive angle plates, one obvious means of preventing platebumping would be to sustain the stock feed flow rate at sufficientlyhigh rates as to preclude cavitation. The solution, however, inheritsthe management difficulties of a minimum flow rate threshold for amachine.

Unfortunately, the flow rate threshold minimum to prevent plate bumpingin open discharge plate refiners is not a fixed quality relative to themachine design and size, exclusively. The wood species and constituencyof the stock blend strongly effect a minimum flow rate value. Forexample, a stock containing percent pine will have a lower minimum flowrate through a particular refiner than a stock containing 15 percentpine.

Stock blend and flow rate flexibility are important economic variablesto the sound management of an integrated, multiple produce, pulp andpaper manufacturing facility. Accordingly, under the state of the priorart, a certain magnitude of managerial discretion is lost chargerefining engines that will greatly reduce the minimum flow thresholdthrough such refiners.

Another object of the present invention is to teach open dischargerefiner plate design characteristics including'a positive angle beaterbars which, in use, will greatly extend the operational life of suchplates.

Another object of the present invention is to teach the construction ofan open discharge refiner plate having an unusually high energy transferefficiency to the stock.

Another object of the present invention is to teach the construction ofa positive angle,open discharge refiner plate requiring an unusually lowapplication of plate pressure for a given magnitude of energy transferto the stock.

SUMMARY OF THE INVENTION These and other objects of the presentinvention are accomplished for low consistency, open discharge platerefiners by providing plates having a positive or pumping angle to thebeater bars thereof in combination with a maximal number of beater bars,sufficient flow resistance along grooves between the beater bars tobalance centrifugal forces on the stock, and an open discharge peripheryat the bar groove terminus but a plugged terminus for stock feed groovesrespective to a pie segment of parallel beater bars in at least one of acoopera-' tive plate set.

Open discharge refiners equipped with plates of the present inventionmay be operated at extremely low plate loading pressures to develop agiven stock freeness. Although comparative lyless energy per weightunitof stock will be consumed by refining engines of the presentinvention, a greater percentage of that energy consumption will betransferred to the fiber objective.

BRIEF DESCRIPTION OF THE DRAWINGS Relative to the drawings wherein likereference characters denominate like elements throughout the severalfigures:

FIG. 1 is a schematic section of an open discharge refiner of a typesuitable for use in the invention combination.

FIG. 2 is a frontal view of a refiner plate segment according to thepresent invention.

FIG. 3 is a sectional portion of the present refiner plate taken fromFIG. 2 atcute line llI-III.

FIG. 4 is a sectional portion of the present refiner plate taken fromFIG. 2 at cut line IV-I\/.

FIG. 5 is a sectional portion of the present refiner plate taken fromFIG. 2 at cut line VV.

FIG. 6 is a frontal view of a refiner plate segment having a modifiedbeater bar and feed groove orientation.

DESCRIPTION OF THE PREFERRED EMBODIMENT Relative to FIG. 1, the opendischarge refiner repre sented therebyis of a single disc type whereinone plate 10 of a cooperative pair is rigidly secured in a station,- aryposition. As shown, the stationary plate 10 is rigidly secured to thestock shroud 11 which in turn, is rigidly secured to the machine frame12.

The rotating plate is secured to rotor disc 21 i which, in turn, issecured to an axially reciprocable, driven shaft 22. Rotational power isdelivered to shaft 22 by a rotor spider 23 portion of motor 24.

Rotor shaft 22 is radially restrained by pedestal bearings25 and 26which are rigidly integrated with the frame 12.1

Rotating and stationary plate proximity and hence, plate pressure, isregulated by means of a threaded shaft 27.

Fiber stock is introduced to the inter-proximal region between plates 10and 20 by an inlet duct 13. The only permissible flow course from thecentral aperture 14 of stationary plate 10 to the unrestricteddischargeduct 15 is between the relatively rotating bar elements of plates 10 and20.,

Although the invention is described relative to a single rotating plate,single disc refiner, it should be understood that'the invention isequally relevant to refiners in which both plates of a cooperative pairare rota-' tively driven.

It is the usualYpractice to assemble each full circle disc of plates 10and 20 from a plurality of structurally independent but identicalcircular segments such as the 45 segment 30 of FIG. 2. Bolts throughcounterbored holes 31 secure each circular segment of the plate to theshroud 11 or rotor disc 21, respectively, in relative alignment.

Relative to FIGS. 2 and 3, both plates of a pair comprise inner andouter annular sections and 50, respectively, separated by a circularstock distribution groove 60. A satisfactory dimensional relationshipbetween the diameters of the distribution groove 60 and the outerperiphery of the outer annular section is a factor of 2, e.g. the outerplate diameter is approximately 2 times the distribution groovediameter.

segregating the annularsections 40 and 50 into ap: proximately 15 radialsections are radial feed grooves 61. Further segregating the annularsection 40 into pairs of 15 sectors are enlarged feed grooves 62extending from the plate inner periphery 32 to the circular feed groove60.

The inner annularsection 40 is often characterized as the breakersection due to the design function of first receiving the radiallyout-flowing stockfrom the inlet duct 13-which, at this point, mayinclude relatively coarse fiber bundle lumps and system accumullatedtrash such as. bits of metal. The inner annular section 40 beater bars41 are approximately half the width of channels 42, representativedimensions for a 44 inch diameter plate being 3/16 inch and /8 inch,respectively. Feed grooves 61 are approximately /8 inch wide whereas theenlarged feed grooves 62 are approximately l inches. I

Depth of the breaker section channels 42 diminishes from 7/16 inchnearthe plate center to 5/16 inch at the circular feed groove 60. I

Relative to the direction of rotation, a feed groove 61 establishes thereference angle for beater bars 41 in the preceding 15 sector 'of theannular section 40. All beater bars 41 and channels 42 preceding arespective feed groove radius are parallel thereto. Consequently, theangle of each bar relative to a local radius progressively increasesfrom to 15. For this reason, it is convenient to refer to an average barangle of 7.5.

Various permutations of factors affecting bar angularity may produce anaverage positive bar angle from to 25".

The outer annular section 50, characterized as the refining sectioncomprises a beater bar angular orientation similar to that of the beatersection. In this section, both, bars 51 and channels 52 are shown byFIG. 4 to be of identical width A at Vs inch respectively. For reasonsof structural strength, a Vs inch bar width is'a near minimum. Since onedesign objective is to provide as many beater bars as possible withinthe allotted area, it is, therefore, preferable to not greatly exceed orreduce this dimension. Channel width, however, is variable, for reasonsto be subsequently explained.

The channel depth is 3/16 inch whereas the feed groove 61 depth is inch.

Although the preferred embodiment of the invention disposes the feedgrooves 61 along a plate radius, such alignment is not absolutelynecessary. FIG. 6 illustrates an embodiment of the invention whereinfeedgrooves 63 are out along a positive angle to the radius as an expedientto increase the average beater bar angle within the preceding 15 sector.Note from this embodiment that the divisional interface 64 betweenadjacent 15 plate segments do not follow the axes of feed grooves 63.Consequently, in the FIG. 6 embodiment, beater bars 51 and channels 52rotatively preceding a respective feed groove 63 have a differentangular orientation from bars and channels on the same segment butfollowing the same feed groove.

The average beater bar angle may also be increased by increasing theangular arc of each radial section.

Specific dimensions are disclosed herein for the purpose of teachingdimensional comparatives for a single embodiment. It shouldbeunderstood, howeverQthat such dimensions are not of a limiting natureand may be altered by those of ordinary skill in the art withoutdeviating from the spirit of the invention.

Noteworthy of the refiner section 50 is the fact that channels 52 arecontinuous and uninterrupted to the outer plate periphery 33. Feedgrooves 61, on the other hand, in at least one of a cooperative platepair, are plugged by peripherial dams 53.

Although many facets of the aforedescribed plate design are known andconventional, the particular combination described herein us unique inthat it maximizes performance from a low consistency, open dischargemachine.

There is also a conventional belief in the paper pulp preparation artthat the mechanics of refining are of a frictional nature. Extensivestudies, however, have revealed this belief to be unfounded in that theenergy transfer mechanism to the stock fiber is by viscous dissipationeg. energy transfer due to the presence of a shear field in a liquidmedium. Such viscous dissipation increases as the gap separation betweenthe plates 10 and 20 decreases.

Plate pressure reflects the magnitude of squeeze film resistance andconsequent pressure between opposite beater bar faces. The size of theindividual area por tions between two respective plate bars is the forcemagnitude determinator for a given squeeze film thickness. Accordingly,the smaller the individual area portions between two respective platebars, the lower is the required plate pressure to maintain the same gapseparation. As previously stated, the gap is the primarily relevantfactor to energy transfer and pressure is merely the consequence of agiven gap for a particular bararea pattern.

To optimize the plate pattern, it therefore follows that the refinersection should be provided with a maximum number of minimum width beaterbars.

An independent factor of relevance to the refiner section bar pattern isthat of channel 52 flow area. The controlling objective of this factoris tobalance the centrifugal force impetus to accelerate the stockmovement along the channels with channel surface flow resistance. Theprimary instrument of flow resistance is channel width. A forcebalancing width, however, will depend on the particular stockcharacteristics and consistency. A A; inch channel width may be adequatefor hardwood'stock whereas a f/t inch width may be more appropriate forpine of the same consistency.

As previously stated, the channel terminus at the outer plate periphery33, however, should be open and unobstructed. On the other hand, thefeed grooves 61 which supply stock to the foreshortened channels 52opening thereinto are completely plugged on at least one plate of thecooperative pair and preferably on the rotor.

The mechanism by which a positive bar angle in an open discharge refiner'will deliver superior refining performance is not completelyunderstood. It is known however, that a primary objective of the priorart negative angle is to impede stock flow between the plate and reducethe minimum, cavitation threshold, flow rate. This objective may beobtained by other means, however, such as plugging the feed grooves 61and minimizing the channel 52 flow area.

ln developmental tests of 44 inch diameter plates for open dischargerefiner engines of the aforedescribed design operated at 500 rpm andhaving a positivebar angle of 7.5 on both, the rotor 20 and stator 10but with the feed grooves 61 on the rotor 20 only plugged, the plate setgave 20 weeks of service on hardwood for a given stock slowness. Stockconsistency was approximately 2-'-6 percent. Plate pressure and energyconsumption was substantially reduced from prior art norms.

The normally expected useful lifespan of prior art plates on thesame'machines working the same stock flow ranges from 5 to 8 weeks.

Having described the preferred embodiment of our invention, it will beapparent that modifications thereof will occur to those skilled in theart within the scope of the apended claims.

We claim:

1. In an open discharge, low consistency, cellulosic stock refiningengine having an unpressurized stock discharge conduit and a cooperativepair of planar, oppositely facing, relatively rotating refining plates,said plates having a circular outer periphery about an axis of rotationand being divided into inner and outer concentric annular sections, saidannular scctions being separated by a circular distribution groove intothe face plane of said plates, said outer annular section being furtherdivided into a plurality of circle sectors, said sectors being separatedby stock feed grooves into the face plane of said plates, said stockfeed grooves extending linearly from said circular distribution grooveto the proximity of said outer periphery, relative to a predeterminedrotational direction for said plates, the improvement comprising:

A. a plurality of alternating parallel beater bars and flow channelsextending across the face plane of said plates within a sector which isdelineated by two angularly successive feed grooves relative to saidrotational direction, the feed groove angularly leading said sectorrelative to said rotational direction being designated as the leadingfeed groove and the feed groove angularly trailingsaid sector relativeto said rotational direction being designated as the lagging feedgroove, said bars and channels within a respective sector beingangularly oriented parallel to the length of said lagging feed groove, anumber of said channels within a respec'-' tive sectorbeing continuouslyopen from said circular distribution groove to said outer plateperiphery, the remainder of said channels within a respecf stockrefining engine having an unpressurized stock discharge conduit and acooperative pair of planar, op-

positely facing, relatively rotating refining plates, said tive sectorbeing continuously open from the re-,-

spective leading feed grooveto said outer plate periphery; and, i B.said feed grooves terminating inwardly from said outer periphery thereofrespective to at least one,

within said channels when said plates are relatively rotating.

6. Apparatus as described by claim 5iwherein said bars and channels areapproximately of equal width.

7. Apparatus as described by claim 5 wherein said channels are ofgreater width than said bars.

8. in an open discharge, low consistency, cellulosic mately equal to thecentrifugal force on said stock plates having a circular outer peripheryabout an axis of rotation and being divided into inner and outerconcentric annular sections, said annular sections being separated by acircular distribution groove into the face a plane of said plates, saidouter annular sections being further divided into a plurality of circlesectors, each of said sectors having an adjacent stock feed groove intosaid plate face plane between adjacent sectors, said feed grooveextending linearly from said distribution groove to the proximity ofsaid outer periphery, relative to a predetermined rotational directionfor said plates, the improvement comprising:

A. each feed groove being disposed at an angle relative to a plateradius passing therethrough whereby the outer peripherial portion of therespective feed groove angularly trails the inner portion thereofrelative to said rotational direction;

B. a plurality of alternating beater bars and flow channels across saidplate face plane within said sectors angularly preceding an adjacentfeed groove relative to said rotational direction and parallel thereto,a number of said channels being continuously open from said distributiongroove to said outer periphery, the remainder of said channels openinginto the feed groove respective to the next 1 adjacent angularlypreceding sector and being continuously open to said outer periphery;and

C. said feed grooves terminating inwardly from said outer peripherythereof respective to at least one plate of a cooperative pair.

9. Apparatus as described by claim 8 wherein the angle of said feedgroove relative to a plate radius isless than l5.. a

10. Apparatus as described by claim 9 wherein one, plate of saidcooperative pair is stationary, said feed grooves in the other, rotatingplate beingplugged inwardly from said outer periphery.

ll. Apparatusv as described by claim 9 wherein the stock flow resistancewithintsaid channels is approxi mately equal to the centrifugal force onsaid stock within said channels when said plates are relativelyrotating.

12. Apparatus as described by claim 11 wherein said bars and channelsareapproximately of equal width.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3,910!Dated October 7, 975

Inventor(s) Philip J. Leider et al.

It is certified that error appears in the above-identified patent andthat said Letters Patent are hereby corrected as shown below:

Column 2, line l-B, following the word "taught" delete "by" and insertin therefor.

Column 5, line 5 l-, following the word "herein" delete the word "us"and insert the word is therefor.

Signed and Sealed this third Day Of February 1976 [SEAL] A ttest:

RUTH C. MASON C. MARSHALL DANN Arresting Officer Commissioner ofPatemsand Trademarks UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTIONPatent No. 5,910,511 Dated October 975 Inventor(s) Philip J. Leider etal.

It is certified that error appears in the above-identified patent andthat said Letters Patent are hereby corrected as shown below:

Column 2, line 5, following the word "taught" delete "by" and insert intherefor.

Column 5, line 5 following the word "herein" delete the word "us" andinsert the word is therefor.

Signed and Scaled this third Day of February 1976 [SEAL] A ttes t:

RUTH C. MASON C. MARSHALL DANN Arresting Officer Commissioner of Patentsand Trademarks

1. In an open discharge, low consistency, cellulosic stock refiningengine having an unpressurized stock discharge conduit and a cooperativepair of planar, oppositely facing, relatively rotating refining plates,said plates having a circular outer periphery about an axis of rotationand being divided into inner and outer concentric annular sections, saidannular sections being separated by a circular distribution groove intothe face plane of said plates, said outer annular section being furtherdivided into a plurality of circle sectors, said sectors being separatedby stock feed grooves into the face plane of said plates, said stockfeed grooves extending linearly from said circular distribution grooveto the proximity of said outer periphery, relative to a predeterminedrotational direction for said plates, the improvement comprising: A. aplurality of alternating parallel beater bars and flow channelsextending across the face plane of said plates within a sector which isdelineated by two angularly successive feed grooves relative to saidrotational direction, the feed groove angularly leading said sectorrelative to said rotational direction being designated as the leadingfeed groove and the feed groove angularly trailing said sector relativeto said rotational direction being designated as the lagging feedgroove, said bars and channels within a respective sector beingangularly oriented parallel to the length of said lagging feed groove, anumber of said channels within a respective sector being continuouslyopen from said circular distribution groove to said outer plateperiphery, the remainder of said channels within a respective sectorbeing continuously open from the respective leading feed groove to saidouter plate periphery; and, B. said feed grooves terminating inwardlyfrom said outer periphery thereof respective to at least one plate of acooperative pair.
 2. Apparatus as described by claim 1 wherein theaverage angle of said bars relative to a plate radius is between 5* and25*.
 3. Apparatus as described by claim 1 wherein said feed grooves areradial.
 4. Apparatus as described by claim 1 wherein one plate of saidcooperative pair is stationary, said feed grooves in the other,rotating, plate being plugged inwardly from said outer periphery. 5.Apparatus as described by claim 1 wherein the stock flow resistancewithin said channels is approximately equal to the centrifugal force onsaid stock within said channels when said plates are relativelyrotating.
 6. Apparatus as described by claim 5 wherein said bars andchannels are approximately of equal width.
 7. Apparatus as described byclaim 5 wherein said channels are of greater width than said bars.
 8. Inan open discharge, low consistency, cellulosic stock refining enginehaving an unpressurized stock discharge conduit and a cooperative pairof planar, oppositely facing, relatively rotating refining plates, saidplates having a circular outer periphery about an axis of rotation andbeing divided into inner and outer concentric annular sections, saidannular sections being separated by a circular distribution groove intothe face plane of said plates, said outer annular sections being furtherdivided into a pluralitY of circle sectors, each of said sectors havingan adjacent stock feed groove into said plate face plane betweenadjacent sectors, said feed groove extending linearly from saiddistribution groove to the proximity of said outer periphery, relativeto a predetermined rotational direction for said plates, the improvementcomprising: A. each feed groove being disposed at an angle relative to aplate radius passing therethrough whereby the outer peripherial portionof the respective feed groove angularly trails the inner portion thereofrelative to said rotational direction; B. a plurality of alternatingbeater bars and flow channels across said plate face plane within saidsectors angularly preceding an adjacent feed groove relative to saidrotational direction and parallel thereto, a number of said channelsbeing continuously open from said distribution groove to said outerperiphery, the remainder of said channels opening into the feed grooverespective to the next adjacent angularly preceding sector and beingcontinuously open to said outer periphery; and C. said feed groovesterminating inwardly from said outer periphery thereof respective to atleast one plate of a cooperative pair.
 9. Apparatus as described byclaim 8 wherein the angle of said feed groove relative to a plate radiusis less than 15*.
 10. Apparatus as described by claim 9 wherein oneplate of said cooperative pair is stationary, said feed grooves in theother, rotating plate being plugged inwardly from said outer periphery.11. Apparatus as described by claim 9 wherein the stock flow resistancewithin said channels is approximately equal to the centrifugal force onsaid stock within said channels when said plates are relativelyrotating.
 12. Apparatus as described by claim 11 wherein said bars andchannels are approximately of equal width.